In recent years, the use of a user terminal capable of connecting not only to a cellular network but also to another network expands. For example, the use of a user terminal (so-called dual terminal) capable of connecting to a cellular network and a wireless LAN (Local Area Network) expands, and therefore, in 3GPP (3rd Generation Partnership Project) which is a project aiming to standardize a cellular communication system, a technology is being considered which is capable of strengthening cooperation between a cellular RAN (Radio Access Network) and a wireless LAN (see Non Patent Document 1).
In such a user terminal, it is possible to switch an accommodation target of traffic of a user terminal from a cellular network to another network. As a result, it is possible to reduce traffic load of a cellular network (offload).